The present invention relates to antenna arrays, and more particularly, to a common aperture dual polarization array fed by rectangular waveguides.
Very high resolution seeker antennas, for example, require fully populated dual polarization antenna arrays. There are several kinds of dual-polarization seeker antenna arrays presently known that are used for such seeker antennas, and upon which the present invention improves. These include a reflector antenna array with a dual polarization feed. The reflector antenna array is bulky and its efficiency is low. Furthermore, reflector antenna array is very difficult to achieve low sidelobe array pattern.
A second antenna array is a patch array antenna. The patch antenna array is low cost and low profile, but its bandwidth of each element is extremely narrow that achieving high performance array with the patch element is very difficult. Also, the efficiency of the patch antenna array is poor.
A third antenna array is a combination antenna array comprising a shunt slot array fed by a rectangular waveguide that provides for vertical polarization, combined with a dipole array fed by a stripline that provides for horizontal polarization. This combination antenna array employs an efficient vertical polarization array, but the dipole array fed by the stripline is bulky. More particularly, control of the input impedance seen at the stripline of each dipole that is required to achieve a low sidelobe pattern is very difficult to achieve, and the overall input match of the array is also very difficult to achieve. However, phase matching between the vertical polarization array and the horizontal polarization array is difficult because each array uses a different transmission line.
Consequently, it is an objective of the present invention to provide for a common aperture dual polarization array fed by rectangular waveguides that improves upon the above-mentioned antenna arrays.